Changes

stp: set up all M3UA ports in array in steps

This way we have all ports in more or less the same state when handling
messages.
It should also speed up tests and mitigate sporadic failures  under some
scenarios where we already accept the SCTP conn instead of rejecting it
and waiting for reconnect from client.

Change-Id: I585d9c768301bfd9ba849876923787137fc35981